Ratcheting of driven attracting colloidal particles: Temporal density oscillations and current multiplicity

TL;DR

This paper investigates how attractive interactions and external ratchet potentials influence particle transport in colloidal suspensions, revealing attraction-induced symmetry breaking, density oscillations, and multiple current states.

Contribution

It introduces a dynamical density functional theory approach to analyze driven colloids with attractive interactions in ratchet potentials, uncovering novel density oscillations and current multiplicity phenomena.

Findings

Attraction strength causes depinning and time-dependent density profiles.

Symmetry breaking leads to coexistence of different density states.

Multiple stable and oscillatory current states are observed.

Abstract

We consider the unidirectional particle transport in a suspension of colloidal particles which interact with each other via a pair potential having a hard-core repulsion plus an attractive tail. The colloids are confined within a long narrow channel and are driven along by a DC or an AC external potential. In addition, the walls of the channel interact with the particles via a ratchet-like periodic potential. We use dynamical density functional theory to compute the average particle current. In the case of DC drive, we show that as the attraction strength between the colloids is increased beyond a critical value, the stationary density distribution of the particles loses its stability leading to depinning and a time dependent density profile. Attraction induced symmetry breaking gives rise to the coexistence of stable stationary density profiles with different spatial periods and time-periodic density profiles, each characterized by different values for the particle current.